The present invention relates to a method for the motion adaptive interpolation of nontransmitted television image sequences formed from at least two transmitted sequences, and to uses for this method. A method of this type is described by Netravali and Robbins in "Motion Adaptive Interpolation of Television Frames"; and by Bergmann in "Motion Adaptive Interpolation of Eliminated TV Fields", both published in Proc. of the Picture Coding Symposium, 1981, Montreal, Canada.
Several proposals have been published for the reduction of the transmission rate of digital television image sequences. These proposals primarily involve the elimination of individual television image sequences, i.e. television fields or frames, at the transmitting end and image interpolation at the receiving end, as described by Netravali et al and Bergmann, supra, as well as by Klie in "Codierung von Fernsehsignalen funiedrige Ubertragungsbitraten" [Coding of Television Signals For Low Transmission Bit Rate], Dissertation, 1978, University of Hannover.
Klie describes a relatively simple interpolation method. The luminance values of picture elements, i.e. pixels, within the eliminated frames are obtained from the corresponding pixels in the transmitted frames. The drawback of this method is that it achieves inadequate reconstruction of moving image portions. A purely linear interpolation leads to smudged contours in the case of slow movements. For fast movements, this type of interpolation leads to multiple displays of the moving image portions resulting in motion reconstruction which appears jerky in the image sequence.
To improve these inadequacies, adaptive interpolation methods have been developed, also described by Netravali et al and Bergmann, supra. Here, the television image to be reconstructed is divided by means of a segmentizer into stationary image and nonstationary image regions. Then each pixel within a nonstationary image region is fed to a displacement estimator to obtain a reference value of the amount of movement. For luminance signal interpolation in the nonstationary image regions, the correspondingly offset pixels from the transmitted images can be used. By means of this interpolation method, the picture quality for small displacement amplitudes can be visibly improved. However, as detailed examinations have shown, this motion adaptive interpolation is unsatisfactory for large displacement amplitudes because of the inaccuracy of the displacement estimator and segmentizer employed.